title: Structure, stability and relaxivity of trinuclear triangular complexes.
abstract: The self-assembly of a carbonylpyridine-based heptadentate ligand with Ln(III) results in the formation of triangular trinuclear europium complexes, which exhibit interesting luminescent properties in the solid state and in solution. With a view to developing multimodal responsive systems, we report here the preparation and characterisation of analogous complexes with Gd(III). The X-ray crystal structure of Gd(3)L2(3) indeed reveals the isostructurality with the Eu(III) complexes. A combination of (1)H NMRD and variable temperature studies yields the parameters elucidating the exchange of coordinated water and relaxivity properties. Conveniently, the competitive spectrophotometric titrations with EDTA and NTA are used to determine the thermodynamic stability constants of the europium complexes in aqueous media. In addition, the exchange reaction with EDTA is monitored with NMR and fluorimetry. The interactions of the Eu(III) trinuclear complex with some potentially interfering ligands are qualitatively investigated by means of luminescence titrations.
authors.affiliation: Department of Inorganic, Analytical and Applied Chemistry University of Geneva, 30 quai E.-Ansermet1211, Geneva, Switzerland.
authors.forename: Soumaila
authors.initials: S
authors.lastname: Zebret
authors.forename: Elena
authors.initials: E
authors.lastname: Torres
authors.forename: Enzo
authors.initials: E
authors.lastname: Terreno
authors.forename: Laure
authors.initials: L
authors.lastname: Guénée
authors.forename: Carmine
authors.initials: C
authors.lastname: Senatore
authors.forename: Josef
authors.initials: J
authors.lastname: Hamacek
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry; D018360:Crystallography, X-Ray; D004492:Edetic Acid / Q000737:chemistry; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D008958:Models, Molecular; D008968:Molecular Conformation; D013816:Thermodynamics
chemical_list: D002264:Carboxylic Acids; D028581:Lanthanoid Series Elements; D004492:Edetic Acid